Methods and apparatus for providing a frequency hopping analog cordless telephone

ABSTRACT

A cordless telephone system comprising a handset and a base station. Each of the handset and the base station contains a transmitter and a receiver, preferably operating on different frequencies. At least one of the handset and the base station controls frequency hopping based on a signal received from the other of the handset and the base station. In a preferred embodiment, The handset transmitter transmits to the base station a combined signal including a digital portion and an analog portion. The base station separates the combined signal to recover the digital portion and the analog portion and employs the analog portion to convey communicated information and the digital portion to control frequency hopping in the transmitter of the base station. The handset transmitter provides a local oscillator signal to the handset receiver to enable frequency conversion in the handset receiver. The base station transmits to the handset a similar combined signal which is similarly separated and employed by the handset.

[0001] The present application is a continuation of U.S. applicationSer. No. 09/164,512 filed Sep. 30, 1998 and incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to improvements tocordless telephony. More particularly, the invention relates toadvantageous apparatus and methods for providing a frequency hoppingcordless telephone.

BACKGROUND OF THE INVENTION

[0003] A typical cordless telephone system includes a base station and ahandset. The base station is typically connected by wire to a centraloffice. The handset communicates with the base station by cordlessmeans, such as through radio frequency signals, without a directphysical connection to the base station. Cordless telephones allowconsiderable freedom and mobility to the user, allowing the user to moveabout while engaged in a call, and to conduct a call at a considerabledistance from the base station. Presently, two preferred cordlesssystems exist, digital and analog. Analog systems provide the advantagesof simplicity, low cost, and high sound quality, but are vulnerable toin-band interference or jamming. Moreover, analog systems may interferewith other telephones. For this reason, analog systems are restricted inpower, resulting in a reduced range.

[0004] Digital systems exist, which have both advantages anddisadvantages with respect to analog systems. Digital systems provide adigital processing gain, reducing susceptibility to in-bandinterference, with the resistance to interference increasing withprocessing gain. Digital systems are less likely to interfere with othertelephone systems, and are permitted greater transmit power than areanalog systems. The combination of greater transmit power and digitalprocessing gain provides digital systems with a significantly greaterrange than is possessed by analog systems. Disadvantages of digitalsystems are a much higher cost due to the need to have powerfulprocessors to perform voice coding and decoding, as well as digitalsignal processing (DSP) to achieve processing gain. Many parts of adigital system transmitter and receiver, such as a modulator anddemodulator, are subject to more stringent requirements than are thecorresponding parts of analog systems, and are therefore morecomplicated. Moreover, digital voice coding, interleaving, and spreadingtake time to perform, delaying signal transmission. Delay is especiallyprevalent in systems employing time domain duplexing, in whichtransmitter and receiver work in turns, half time each. This delay isadded to the delay caused by digital processing, and may create aproblem called echo. Echo in digital systems produces a significantdegradation of sound quality, with the amount and nature of thedegradation being influenced by the amount of delay and the spectrumcontent of the reflection. Echo cancellation in digital systems of theprior art represents a considerable challenge and increases the cost ofthe system.

[0005] An important aspect of transmission in cordless telephone systemsis spreading. Systems of the prior art commonly use one of twotechniques. These techniques are direct sequence and frequency hopping.In direct sequence systems the information signal is multiplied by apseudo-random sequence of bits, widening the spectrum of the resultingsignal. The received signal is multiplied with the same sequence onceagain to despread it. Many well-known techniques exist for performingspreading and despreading.

[0006] In frequency hopping systems, information bits are grouped intoframes. Each frame is transmitted on a different carrier frequency. Overa period of time, therefore, the energy of the signal is spreadthroughout the entire bandwidth. Frequency hopping systems areappropriate for a time division duplexed system (“TDD”), since thetransmitter and receiver of a TDD must be rapidly switched on and off.The transmitter and receiver of a TDD employing a frequency hoppingsystem repeat an on-off cycle, with each repetition of the cycleemploying a different frequency. A TDD employing frequency hopping isparticularly vulnerable to echo.

[0007] It is possible to combine direct sequence and frequency hoppingspreading techniques. A system using these combined techniques wouldhave a large processing gain and a high interference immunity, but wouldbe complex and expensive. Due to an extensive processing and hoppingdelay, it would also be susceptible to echo.

[0008] A need therefore exists in the art for a cordless telephonesystem with a low cost, high processing gain with resulting highinterference immunity, and resistance to echo.

SUMMARY OF THE INVENTION

[0009] A cordless telephone according to the present invention includesa handset and a base station wherein frequency hopping is controlled inat least one of the handset and the base station by a signal receivedfrom the other of the handset and the base station. Preferably the basestation and the handset each have a transmitter and a receiver operatingsimultaneously on different frequencies. The handset performs frequencyhopping according to information contained in a signal received from thebase station and the base station performs frequency-hopping accordingto information in a signal received from the handset. Preferably, thefrequency-hopping information is transmitted in a single signal togetherwith user information, such as a voice communication to be transmittedby the handset.

[0010] In a preferred embodiment of the invention, the handset transmitsto the base station a modulated carrier signal comprising a digitalportion and an analog portion. The base station receiver receives thesignal and demodulates it to recover the digital portion and the analogportion. The analog portion is employed to provide user information,while the digital portion is employed to generate a hopping controlsignal used to control frequency hopping by the base stationtransmitter. The base station transmitter also employs the hoppingcontrol signal to produce a local oscillator signal used to controlfrequency conversion in the base station receiver. Similarly, the basestation transmits to the handset a modulated carrier signal containing adigital portion and an analog portion. The handset recovers the digitalportion and the analog portion and employs the analog portion to provideuser information, while employing the digital portion to controlfrequency hopping in the handset transmitter and receiver. The handsetand base station employ the digital portions of the signals to providefor frequency hopping without an interruption of communication.

[0011] A cordless telephone according to the present invention includesadvantages of an analog cordless telephone, together with processinggain and spread spectrum capabilities, having resistance to echo and acost significantly below that of prior-art digital techniques. Thecombination of analog modulation and digital data provides frequencyhopping without an interruption of communication.

[0012] A more complete understanding of the present invention, as wellas further features and advantages of the invention, will be apparentfrom the following Detailed Description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a prior art cordless telephone system;

[0014]FIG. 2 illustrates a handset and base station for use in acordless telephone system according to the present invention;

[0015]FIG. 3 illustrates a modulated carrier signal preferably employedby a cordless telephone system according to the present invention;

[0016]FIG. 4 illustrates a transmitter for use in a cordless telephonesystem according to the present invention;

[0017]FIG. 5 is a frequency plan preferably used by a handset of acordless telephone system according to the present invention;

[0018]FIG. 6 is a frequency plan which may be used by a base station ofa cordless telephone system according to the present invention;

[0019]FIG. 7 is a flowchart illustrating the steps of a method forfrequency-hopping cordless telephony according to the present invention;and

[0020]FIG. 8 is a flowchart illustrating the steps of an alternativemethod for frequency-hopping cordless telephony according to the presentinvention.

DETAILED DESCRIPTION

[0021]FIG. 1 illustrates a cordless telephone system 100 according tothe prior art. The telephone system 100 includes a handset 102 and abase station 104. The handset 102 includes a transmission section 106and a reception section 108. The transmission section 106 includes amicrophone 110, which receives voice inputs from the user and produces avoice signal which is then passed to a voice coder 112. The voice coder112 produces a coded signal which is then passed to an interleaver 114.The interleaver 114 produces an interleaved signal which is passed to aspreader 116. The spreader 1 16 spreads the interleaved signal toproduce a spread signal, and passes the spread signal to a pulse shaper118. The pulse shaper 118 produces a pulse-shaped signal which is thenpassed to a transmitter 120 for transmission to the base station.

[0022] The reception section 108 includes a receiver 124. The receiver124 receives a transmission from the base station 104 to produce areceived signal which is then passed to a despreader 126 to produce adespread signal. The despread signal is passed to a deinterleaver 128,which produces a deinterleaved signal and passes the deinterleavedsignal to a voice decoder 130. The voice decoder 130 produces a voicedecoded signal which is then passed to a loudspeaker 132, which producesaudible sounds which can be heard by a user.

[0023] The base station 104 includes a transmission section 122 similarto the transmission section 106, which produces a signal for receptionby the reception section 108 of the handset. The transmission section122 includes a voice coder 134, an interleaver 136, a spreader 138, apulse shaper 140, and a transmitter 142. The base station 104 alsoincludes a reception section 143, which includes a receiver 144,despreader 146, deinterleaver 148, and voice decoder 150. Thetransmission section 122 operates similarly to the transmission section106 of the handset 102, and the reception section 142 operates similarlyto the reception section 108 of the handset 102. The transmissionsection 122 does not include a microphone, and the reception section 142does not include a loudspeaker. Instead, the base station includes aline interface 152 which passes signals to and from a central telephoneoffice (not shown). When the base station 104 receives a signal from thehandset 102, the signal is processed by the reception section 142 (beingsubject to normal processing delays) and passed to the line interface152. A portion of the signal is reflected from the telephone line (notshown) to the line interface 152 and passed along the transmissionsection 122, being subjected to similar processing delays. The delaysresult in an echo which is heard in the loudspeaker 132.

[0024] Analog telephones are subject to a reflection from the telephoneline, but as analog telephones are not subject to processing delays,this reflection is much less harmful to analog telephone operation thanto digital telephone operation.

[0025]FIG. 2 illustrates a cordless telephone system 200 according tothe present invention. The telephone system 200 includes a handset 201and a base station 202. The handset 201 includes a microphone 203, afirst control data unit 204, and a first signal combiner 206. The firstmicrophone 203 provides a first analog signal to the first signalcombiner 206, which also receives a first digital signal, used as acontrol data signal, from the control data unit 204. The first signalcombiner 206 combines the first analog signal and the first control datasignal to produce a first combined signal. The handset 200 furtherincludes a first transmitter 208, a first control unit 210, a firstsignal separator 212, a first receiver 214, a first duplexer 216, afirst antenna 218 and a loudspeaker 220. The first transmitter 208receives the first combined signal from the first signal combiner 206,employing the first combined signal as a first modulation input signal.The first transmitter 208 receives a first hopping control signal forcontrol of frequency hopping. The first transmitter 208 produces a firstlocal oscillator signal, the first local oscillator signal preferablybeing an unmodulated signal, and being employed as a first localoscillator output, and a first modulated carrier signal, employed as amodulated carrier output. Modulation of the first modulated carriersignal is accomplished using the first modulation input signal receivedfrom the first signal combiner 206. The first modulated carrier signalthus includes a digital information and analog information. The firstmodulated carrier signal is received by the first duplexer 216, whichpasses the first modulated carrier signal to the first antenna 218 fortransmission to the base station 202, while allowing the simultaneousreception of a second modulated carrier signal, similar to the firstmodulated carrier signal, transmitted from the base station 202 andreceived at the first antenna 218. The first receiver 214 employs thesecond modulated carrier signal received from the base station 202 anddemodulates the second modulated carrier signal to produce a firstdemodulated signal, used as a first demodulated output. The firstreceiver 214 employs the first local oscillator signal from the firsttransmitter 208 as a local oscillator input, and employs the localoscillator input for frequency conversion in the first receiver 214. Thefirst demodulated signal is provided to the first signal separator 212,which produces a first analog output signal which is provided to theloudspeaker 220, and a first digital output signal, employed as a datasignal, which is supplied to the first control unit 210. The firstcontrol unit 210 produces the first hopping control signal which isprovided to the transmitter 208.

[0026] The base station 202 includes a line interface 222, whichreceives a line input and produces a line output. The base stationfurther includes a second control data unit 224 and a second signalcombiner 226. The line output of the line interface 222 is provided asan input signal to the second signal combiner 226. The base station 202further includes a second transmitter 228, a second control unit 230, asecond signal separator 232, a second receiver 234, a second duplexer236, and a second antenna 238. The second signal separator 232 providesa second analog output signal as the line input to the line interface222. The base station 202 operates similarly to the handset 201described above, except that the microphone 203 of the handset 201 isreplaced in the base station 202 by the output of the line interface222, and the loudspeaker 220 of the handset 201 is replaced in the basestation 202 by the input to the line interface 222. The base station 202employs the output from the line interface 222 as a second analogsignal, and a second digital signal, to produce a second combined signalemployed as a second modulation input signal which is provided to thesecond transmitter 228 for use in producing the second modulated carriersignal. The second transmitter 228 also produces a second localoscillator signal, which is preferably an unmodulated signal, and whichis provided to the second receiver 234 as a second local oscillatorinput to enable frequency conversion in the second receiver 234. Thesecond receiver 234 receives the first modulated carrier signal from thehandset 201 and demodulates it to produce a second demodulated signal.The second demodulated signal is provided to the second signal separator232, which produces a second analog output signal which is provided tothe line interface 222, and a second digital output signal, employed asa second data signal, which is supplied to the second control unit 230.The second control unit 230 produces a second hopping control signalwhich is provided to the second transmitter 228.

[0027] Once communication is established between the handset 201 and thebase station 202, the first transmitter 208 and the first receiver 214operate simultaneously on different carrier frequencies. The firsttransmitter 208 receives the first combined signal as the firstmodulation input signal, as noted above. The first modulation inputsignal contains the first analog signal and the first data signal. Theoperation of the first transmitter 208 is controlled by the firstcontrol unit 210, which provides the first hopping control signal to thefirst transmitter 208. The first hopping control signal is based ondigital information contained in the digital portion of the secondmodulated carrier signal received from the base station 202. The firstcontrol unit 210 may also be employed to provide data to the firstsignal combiner 206, in which case the first control data unit 204 isunnecessary. The first transmitter 208 generates the first modulatedcarrier signal, which is modulated through the use of the combinedsignal produced by the first signal combiner 206, provided to the firsttransmitter 208 as the first modulation input signal. The firsttransmitter 208 also generates the first local oscillator signal toenable a frequency conversion in the first receiver 214. Typically,frequency conversion is a down conversion, but frequency conversion maybe accomplished in any of a number of ways commonly known in the art. Asnoted above, the first receiver 214 receives the second modulatedcarrier signal from the base station 202 and demodulates it. The firstdemodulated signal produced by the first receiver 214 by demodulatingthe second modulated carrier signal from the base station 202, has thesame structure as the first modulation input signal described above,containing an analog portion containing user information and a digitalportion containing frequency control data. The base station 202 operatessimultaneously with, and in a similar fashion to, the handset 201.

[0028] The principle of a telephone system according to the presentinvention, such as the telephone system 200 illustrated in FIG. 2, isthat in the handset the first modulated carrier signal and the firstlocal oscillator signal hop simultaneously or very close tosimultaneously, for example within a few microseconds. Similarly in thebase station, the second modulated carrier signal and the second localoscillator signal also hop simultaneously or very close tosimultaneously. The hopping interrupts the audio signal, but so brieflythat the interruption is not noticed. Synchronization between basestation and handset must be as close as possible, and the digital datatransmitted together with the analog signal provides the controlnecessary to provide such close synchronization. Since the base station202 and the handset 201 can send data simultaneously, it is well knownto those skilled in the art how to use the data transferred between thebase station 202 and the handset 201, as taught in the presentinvention, to synchronize the moment of frequency change. It isimportant to note that generation of the new frequency must be as quickas the synchronization itself, and for this reason traditional methodsof generating a frequency signal (for example, phase locked loopfrequency synthesizers with voltage controlled oscillators) are notacceptable. A typical phase locked loop takes a relatively long time toretune, on the order of hundreds of microseconds. Additionally, retuningof a phase locked loop will create a frequency sweep resulting in strongpulses at receiver outputs and will also cause interference to allfrequencies through which it sweeps. The first and second modulatedcarrier signals and the first and second local oscillator signals maypreferably be generated using direct digital synthesis (“DDS”) or asimilar approach which allows sufficiently rapid frequency generation.DDS and other presently known techniques allow synchronization of 1microsecond or better. Also, a combination of techniques could be used,such as using DDS for generating a hopping sequence and mixing it withanother frequency source to obtain the final frequency value.Alternatively, any harmonic of any of the sources could be used.Modulation could be applied to any of the sources.

[0029]FIG. 3 illustrates the structure of a signal spectrum 300 suitablyused as a first modulation input signal or a second modulated inputsignal employed by a telephone system according to the presentinvention. The base-band signal spectrum 300 is formed from an analogsignal spectrum 302 and a digital data spectrum 304. The digital dataspectrum 304 is multiplied by a spreading signal spectrum 306, and alsoby a multiplier 308, to produce a spread data spectrum 310 above thehighest frequency of the analog signal spectrum 302. The spread dataspectrum 310 is combined with the analog signal spectrum 302 to producethe base-band signal spectrum 300. The simplest implementation ofspreading is Manchester coding, but more complex spreading schemes areknown in the art and may also be suitably implemented. Alternatively,the data may be arranged to have the needed spectrum without requiringspreading. Moreover, if a different method is developed which allows thespectra to overlap but still be successfully combined and separated,such a method could be used to create the combined analog-digitalsignal. The analog signal spectrum may theoretically have a lowfrequency as low as 0 Hz, although in present-day practical telephonysystems such a spectrum is not used.

[0030]FIG. 4 is a functional diagram of a transmitter section 400 whichmay suitably be used as the first transmitter 208 in the handset of FIG.2. The transmitter section 400 may similarly be used as the secondtransmitter 228 in the base station of FIG. 2, but to avoid duplicationonly its use as the first transmitter 208 will be discussed. Thetransmitter section 400 produces the first modulated carrier signaldiscussed above in connection with FIG. 2, and the second modulatedcarrier signal produced by the base station 202 is used to controlfrequency hopping by the transmitter section 400. The first modulatedcarrier signal has a variable frequency designated here by TX_(h). Thesecond modulated carrier signal has a variable frequency designated hereby RX_(h). The transmitter section 400 includes a first oscillator 402,which receives a first modulation input signal and produces a firstoscillator signal having a variable frequency designated here by F1. Thetransmitter section 400 further includes a second oscillator 404 whichproduces a second oscillator signal having a variable frequencydesignated here by F2. The transmitter section 400 also includes a DDSgenerator 406, which receives the hopping control signal and produces ahopping signal having a variable frequency designated here by H. Thefrequency range and number of steps of the DDS generator 406 aredictated by overall system requirements and the needed frequency rangewhich must be covered for the frequency TX_(h) of the first modulatedcarrier signal and the frequency RX_(h) of the second modulated carriersignal produced by the base station 202 and used to control frequencyhopping by the handset 202, as well as cost considerations. Thetransmitter section 400 further includes a second oscillator 404, whichproduces a second oscillator signal having a variable frequencydesignated here by F2, a first mixer 408 which mixes the secondoscillator signal and the hopping control signal while providing imagesuppression, and an n-times multiplier 410, which produces a first localoscillator signal having a variable frequency designated here by LO. Thefrequency F2 of the second oscillator signal is chosen so that (F2+H)×nis equal to the desired value of LO. This is the frequency of the firstlocal oscillator signal produced by the transmitter section 400 and usedto control frequency hopping by the first receiver. Also, the range of Hfrequencies needs to be such that when H goes from its lowest to highestvalue, the nth harmonic of (F2+H) covers the whole range of localoscillator frequencies. The transmitter section 400 further includes asecond mixer 412. The second mixer 412 receives the first oscillatorsignal and produces the first modulated carrier signal. Also shown, butnot part of the transmitter section 400, are a duplexer 414, a thirdmixer 416 and an antenna 418. The antenna 418 transmits the firstmodulated carrier signal from the handset and receives the secondmodulated carrier signal from the base station. The duplexer 414receives the second modulated carrier signal from the antenna 418 andpasses it to the third mixer 416, while simultaneously passing the firstmodulated carrier signal from the second mixer 412 to the antenna 418.The third mixer 416 receives the first local oscillator signal from then-times multiplier 410 and combines it with the second modulated carriersignal to produce an IF output signal having a variable frequencydesignated here by IF. The IF output signal may be passed to ademodulator (not shown), or alternatively may be passed to another mixer(not shown) to perform a second frequency conversion beforedemodulation. Either alternative may be suitably employed in accordancewith the present invention, with the choice of alternatives beingdictated by particular design requirements.

[0031]FIG. 5 is a graph 500 illustrating an overall frequency plan for ahandset according to the present invention, with relative values shownfor H, F2, F2+H, LO, TX_(h), RX_(h), F1, and IF. The frequency TX_(h) isthe frequency of the first modulated carrier signal, which istransmitted by the handset to the base station. The frequency RX_(h) isthe frequency of the second modulated carrier signal, which is receivedby the handset from the base station. The graph 500 illustrates aconfiguration employing a low side injection for TX_(h) and RX_(h). Thefrequency range of TX_(h) is higher than the frequency range for RX_(h).The frequency F1 is the difference between LO and TX_(h), while thefrequency IF is the difference between LO and RX_(h). However, a highside injection could be used for both RX_(h) and TX_(h), as well as anycombination such as low side for RX_(h) and high side for TX_(h). Therange for H frequencies is typically relatively low, on the order ofhundreds of kHz. F2 is typically on the order of tens of MHz, as are F1and IF. Frequency ranges for LO, TX_(h) and RX_(h) are equal. In theunlicensed 900 MHz band typically employed for cordless telephonesystems, the ranges for LO, TX_(h) and RX_(h) are typically 10-12 MHz.

[0032]FIG. 6 is a graph 600 illustrating an overall frequency plan for abase station according to the present invention, with relative valuesshown for H, F2, F2+H, LO, TX_(b), RX_(b), F1, and IF. In the case ofthe base station, RX_(b) is the frequency of the first modulated carriersignal received by the handset from the base station, and has the samevalue as TX_(h) described in FIG. 5. The frequency TX_(b) is thefrequency of the second modulated carrier signal transmitted by the basestation to the handset, and has the same value as RX_(h) describedabove. Because TX_(b) and RX_(b) represent the same frequencies as doRX_(h) and TX_(h), respectively, the frequency ranges for TX_(b) andRX_(b) are reversed with respect to TX_(h) and TX_(h). The frequencyrange of RX_(b) is higher than the frequency range for TX_(b). As withthe frequency plan of FIG. 5, the frequency F1 is the difference betweenLO and TX_(b), while the frequency IF is the difference between LO andRX_(b). However, in the frequency plan of FIG. 6, the frequency IF isgreater than the frequency F1.

[0033]FIG. 7 is a flowchart illustrating the steps of a method 700 forcordless telephony according to the present invention. At step 702,communication is established between a handset and a base station, suchas the handset 201 and the base station 202 of FIG. 2. The handset andthe base station transmit analog signals for communication of userinformation. At step 704, the handset produces a first control signalfor control of frequency hopping in the base station. The first controlsignal may suitably be combined with a first communications signal fortransmitting user information to the base station to form a firstcombined signal. The first communications signal an analog signal, whilethe first control signal may be an analog or a digital signal. At step706, the handset transmits the first control signal to the base station,either together with the first communications signal as part of a firstcombined signal, or separately from the first communications signal,depending on design choice. At step 708, the base station employs thefirst control signal to control frequency hopping by the base station.At step 710, the base station produces a second control signal forcontrol of frequency hopping in the handset. The second control signalmay suitably be combined with a second communications signal fortransmitting user information to the handset to form a second combinedsignal. The second communications signal is preferably an analog signal,while the second control signal may be an analog or a digital signal. Atstep 712, the base station transmits the second control signal to thehandset, either together with the second communications signal as partof a second combined signal, or separately from the secondcommunications signal, depending on design choice. At step 714, thehandset employs the second control signal to control frequency hoppingby the handset.

[0034] Steps 704-714 of the method 700 need not and typically may not beexecuted sequentially. For example, steps 704-708 are executed when thehandset transmits a message to the base station, and steps 710-714 areexecuted when the base station transmits a message to the handset.

[0035]FIG. 8 is a flowchart illustrating the steps of an alternativemethod 800 for cordless telephony according to the present invention. Atstep 802, communication is established between a handset and a basestation, such as handset 201 and base station 202 of FIG. 2. At step804, the handset combines a first analog signal with a first digitalsignal to form a combined signal. At step 806, the handset transmits thecombined signal to the base station. At step 808, the base stationreceives the combined signal and separates the combined signal torecover the first analog signal and the first digital signal. At step810, the base station processes the first analog signal to produce anoutput for a user. At step 812, the base station employs the firstdigital signal to control frequency hopping by the base station. At step814, the base station combines a second analog signal with a seconddigital signal to form a second combined signal. At step 816, the basestation transmits the second combined signal to the handset. At step818, the handset receives the second combined signal and separates thesecond combined signal to recover the second analog signal and thesecond digital signal. At step 820, the handset processes the secondanalog signal to produce output for a user. At step 822, the handsetemploys the second digital signal to control frequency hopping by thehandset.

[0036] Steps 804-822 of the method 800 need not and typically may not beexecuted sequentially. For example, steps 804-812 are executed when thehandset transmits a message to the base station, and steps 814-822 areexecuted when the base station transmits a message to the handset.

[0037] While the present invention is disclosed in the context of apresently preferred embodiment, it will be recognized that a widevariety of implementations may be employed by persons of ordinary skillin the art consistent with the above discussion and the claims whichfollow below. For example, although the preferred embodiment employs asignal having a digital component to control frequency hopping and ananalog component to transmit user information, it will be noted that atelephone system according to the invention may be constructed whichemploys a signal using an analog component for the control of frequencyhopping.

I claim:
 1. A cordless telephone system comprising: a handset comprisinga first transmitter and a first receiver, the first transmittertransmitting a first combined signal comprising a first digital portionand a first analog portion, the first analog portion comprising voicedata transmitted from the handset to a base station, the first receiverreceiving from the base station a second combined signal comprising asecond digital portion and a second analog portion, the second analogportion comprising voice data received from the base station, the seconddigital portion comprising frequency hopping data directly controllingthe timing of the frequency hopping and the frequencies used by thehandset; and the base station including a second transmitter and asecond receiver, the second transmitter transmitting the second combinedsignal comprising the second digital portion and the second analogportion, the second analog portion comprising voice data transmittedfrom the base station to the handset, the second receiver receiving fromthe handset the first combined signal comprising the first digitalportion and the first analog portion, the first analog portioncomprising the voice data received from the handset, the first digitalportion comprising frequency hopping data directly controlling thetiming of the frequency hopping and the frequencies used by the basestation.
 2. The cordless telephone system of claim 1 wherein the firsttransmitter and the first receiver change frequency essentiallysimultaneously.
 3. The cordless telephone system of claim 2 wherein thesecond transmitter and the second receiver change frequency essentiallysimultaneously.
 4. The cordless telephone system of claim 3 wherein eachof the first communication signal and the second communication signal isa modulated carrier signal.
 5. The cordless telephone system of claim 4wherein the frequency hopping information is digital data.
 6. Thecordless telephone system of claim 5 wherein the handset includes adirect digital synthesis generator operative to produce a signal havinga rapidly changeable frequency to allow essentially simultaneousfrequency change for the first transmitter and the first receiver. 7.The cordless telephone system of claim 6 wherein the base stationincludes a direct digital synthesis generator producing a signal havinga rapidly changeable frequency to allow essentially simultaneousfrequency change for the second transmitter and the second receiver. 8.The cordless telephone system of claim 7 wherein the handset includes adirect digital synthesis generator producing a signal having a rapidlychangeable frequency to allow essentially simultaneous frequency changefor the first transmitter and the first receiver.
 9. The cordlesstelephone system of claim 1 wherein the frequency hopping data comprises10. A handset for use in a cordless telephone system comprising: areceiver; and a transmitter, the transmitter transmitting a firstmodulated carrier signal comprising a first digital portion and a firstanalog portion, the first analog portion comprising voice datatransmitted from the handset to a base station, the first digitalportion comprising frequency hopping data directly controlling thetiming of the frequency hopping and the frequencies used by the basestation, the first receiver receiving from the base station a secondmodulated carrier signal comprising a second digital portion and asecond analog portion, the second analog portion comprising voice datareceived from the base station, the second digital output portioncomprising frequency hopping data directly controlling the timing of thefrequency hopping and the frequencies used by the handset.
 11. Thehandset of claim 10 further comprising: a signal combiner receiving ananalog signal and a control data signal to form a modulation inputsignal utilized by the transmitter to produce the first modulatedcarrier signal, the analog signal comprising voice data and the controldata signal comprising the frequency hopping data.
 12. The handset ofclaim 11 wherein the receiver further comprises: a demodulator todemodulate the second modulated carrier signal received from the basestation to produce a demodulated signal; and wherein the handset furtherincludes a signal separator receiving the demodulated signal andproducing a analog output signal utilized to operate a loudspeaker toproduce user output, the signal separator being further operative toproduce a digital output signal and pass the digital output signal to acontrol unit, the control unit being operative to produce a hoppingcontrol signal based on the digital output signal, and wherein thetransmitter is operative to receive the hopping control signal as ahopping control input and change frequencies based on the hoppingcontrol input.
 13. A base station for use in a cordless telephone systemcomprising: a receiver; and a transmitter, the transmitter transmittinga first modulated carrier signal comprising a first digital portion anda first analog portion, the first analog portion comprising voice datatransmitted from the base station to a handset, the first digitalportion comprising frequency hopping data directly controlling thetiming of the frequency hopping and the frequencies used by the handset,the first receiver receiving from the base station a second modulatedcarrier signal comprising a second digital portion and a second analogportion, the second analog portion comprising voice data received fromthe handset, the second digital output portion comprising frequencyhopping data directly controlling the timing of the frequency hoppingand the frequencies used by the base station.
 14. The base station ofclaim 13 further comprising: a signal combiner receiving an analogsignal and a control data signal to form a modulation input signalutilized by the transmitter to produce the modulated carrier signal, theanalog signal comprising voice data and the control data signalcomprising the frequency hopping data.
 15. The base station of claim 14wherein the receiver further comprises: a demodulator to demodulate thesecond modulated carrier signal received from the base station toproduce a demodulated signal; and wherein the handset further includes asignal separator receiving the demodulated signal and producing a analogoutput signal utilized to operate a loudspeaker to produce user output,the signal separator being further operative to produce a digital outputsignal and pass the digital output signal to a control unit, the controlunit being operative to produce a hopping control signal based on thedigital output signal, and wherein the transmitter is operative toreceive the hopping control signal as a hopping control input and changefrequencies based on the hopping control input.
 16. A method offrequency-hopping cordless telephony comprising the steps of:establishing communication between a base station and a handset;transmitting a combined signal from the base station to the handset, thecombined signal comprising an analog portion and a digital portion;processing the combined signal at the handset to recover an analogsignal and a digital signal; producing audio output at the handsetutilizing the analog signal; and employing the digital signal to controlfrequency hopping by a transmitter and a receiver of the handset, thedigital signal including information directing the timing of frequencyhopping and the frequencies to be used by the handset.
 17. The method ofclaim 16 and further comprising the steps of: transmitting a secondcombined signal from the handset to the base station, the secondcombined signal comprising a second analog portion and a second digitalportion; processing the second combined signal at the base station torecover a second analog signal and a second digital signal; transmittingthe second analog signal over a telephone network; and employing thesecond digital signal to control frequency hopping by a transmitter anda receiver of the base station, the second digital signal includinginformation directing the timing of frequency hopping and thefrequencies to be used by the base station.